A device of this kind is known from German Offenlegungsschrift No. 27 13 581. The diaphragm device thereof comprises a slit-shaped aperture, the principal dimension of which extends in a direction approximately perpendicularly to the primary beam. The detector device comprises a series of detectors which are arranged behind the diaphragm device. Each detector can be struck only by the scattered radiation which is generated in a given part of the primary beam, so that a given part of the object is associated with each detector. The detectors together measure the path of the primary beam in the object. The invention can also be used in devices where the diaphragm device is a multi-channel diaphragm as described in German Offenlegungsschrift No. 26 55 230. Instead of a detector device consisting of many separate detectors, use can also be made of a different type of location-sensitive detection device, for example, a gamma camera or an X-ray image intensifier. It is important that an unambiguous spatial relationship exists between parts of the path of the primary beam on the one side and separately readable parts of the detector device on the other side.
For a given path of the primary beam through the object to be examined, only the scattered radiation in this path can be measured. Therefore, it is necessary to change the path of the primary beam with respect to the object in order to measure the scattered radiation in a slice of the object. In all known devices this is done transversely to the primary beam.